1. Field of the Invention
The present invention relates to a method for producing a semiconductor optical device.
2. Related Background Art
Crystal growth like the metalorganic chemical vapor deposition (MOCVD) is widely used for forming each of semiconductor layers constituting a semiconductor optical device. In this crystal growth, there are cases where undesirable particle contaminations (flakes) originating from products or the like adhering to an inner wall or the like of a growth furnace appear on surfaces of the semiconductor layers. If semiconductor layers are further deposited on such flakes, particle contaminations might abnormally grow with the flakes as nuclei.
If the production process is advanced with the particle contaminations being left as they are, they could cause such inconvenience that the After removing the insulating layer 6 and the cap layer 5, the third epitaxial growth step is done particle contaminations hit a mask used in photolithography to crack a wafer, or that broken particle contaminations scatter to contaminate the surfaces of the semiconductor layers. For avoiding it, for example, Patent Document 1 describes a production method of a semiconductor optical device in which the surface of the wafer is treated with nitric acid after the first epitaxial crystal growth by MOCVD, to remove the particle contaminations from the surface of the semiconductor layer. It also describes that etching of the wafer itself is prevented by providing a dummy layer on the surface of the semiconductor layer prior to the nitric acid treatment (cf. FIG. 5 in Patent Document 1).    [Patent Document 1] Japanese Patent Application Laid-open No. 9-51143